The present invention generally relates to load-lifting arrangements and, more particularly, to vertically adjustable car seats.
Car seats with vertical adjustment capability are known in the automobile industry. The seat portion is connected to a pair of carrier members which are in turn articulately connected to a pair of base members by support legs. An actuating handle is operative for moving the carrier members between lowered and raised positions relative to the base members.
It has been proposed to arrange a gear segment for concentric rotation about the pivot axis of the pivotable support legs provided at the rear of the seat. The pivotable support legs at the front of the seat, together with a hinge whose free end is connected to the seat portion of the seat, guide a pinion coaxially about the aforementioned pivot axis. The teeth of the pinion rotatably mesh with the teeth of the gear segment, thereby adjusting the position of the carrier members relative to the base members between a lowered and a raised position.
The known adjustable seat includes two pivotable support legs which are adjacent each other at the front of the seat, and another two pivotable support legs which are adjacent each other at the rear of the seat. All support legs are simultaneously pivotable along a vertical plane.
It is also known to mount the one or two pivotable front support legs for movement about a horizontal axis, and to mount the rear of the seat on guide rails which extend either horizontally or along curved or inclined paths.
The known adjustable car seats which are concentrically arranged gear segments and pinions are characterized in that the annular distance through which the support legs are moved corresponds to the angular distance through which the pinions and gear segments move. The known car seats have the disadvantage that the torque necessary for turning the actuating handle is relatively high when the carrier members are closest to the base members, that is when the carrier members are in their lowered position, and further that the torque is relatively low when the carrier members are furthest from the base members, that is when the carrier members are in their raised position. Therefore, when the actuating handle is turned, the magnitude of the turning torque is continuously varying, and the torque required at any particular time will depend upon the relative position between the carrier and base members. This changing torque characteristic is highly disadvantageous for a user.